This project seeks to determine the organization of the dorsal column system in one group of reptiles, Caiman crocodilus. Experimental and descriptive morphologic techniques will be used to determine ascending connections beginning perpherally at the level of the dorsal root ganglion and proceeding centrally to the telencephalon. These proposed studies will be the first detailed account of the dorsal column system in a single species in any class of vertebrates other than mammals. As such, the data derived from these studies will be of interest to comparative neurobiologists as well as to those scientists interested in somatosensation, in particular, and sensory systems, in general. The proposed experiments will provide answers to several important questions. First, is non-facial somatosensation organized separately from vision and audition in Caiman? Second, are there similarities in neural circuitry of ascending somatosensory systems that parallel those found previously for audition and vision? Comparison with data available from other reptilian species as well as that reported for birds and mammals will be important in understanding somatosensory system organization and evolution in amniotes.